It is legal for the lender of the seven-day cash loan to have the loan qualification, and the loan interest rate shall not exceed 4 times the quoted interest rate of the one-year loan market when the contract is established; It is illegal if the lender is not qualified to lend or its interest rate belongs to usury. Article 680 of the Civil Code prohibits high-interest lending, and the lending rate shall not violate the relevant provisions of the state. If there is no agreement on the payment of interest in the loan contract, it shall be deemed that there is no interest. If the loan contract does not specify the payment method of interest, and the parties cannot reach a supplementary agreement, the interest shall be determined according to the local or the parties' trading methods, trading habits, market interest rates and other factors; Loans between natural persons are regarded as interest-free.